Why the third trimester feels harder on the body and what genuinely helps
Nicola Tik
By the third trimester, the body has been adapting to pregnancy for six months or more, and those adaptations are now at their most pronounced. The bump is larger, the weight distribution has shifted significantly, sleep is often more disrupted, and everyday tasks that felt manageable in the second trimester can start to feel considerably more effortful. This is not a sign that anything is wrong. It is the body working harder than it has ever worked, and understanding what is driving that effort makes it easier to respond to it well. This article looks at what is happening physically in the third trimester, how it differs from the second, and what genuinely helps with the MSK discomfort that many people experience during this phase.
The second trimester tends to be the most physically settled period of pregnancy for many people. The postural changes are underway but not yet at their most demanding, and energy levels are often better than in the first or third trimester. The third trimester shifts that balance considerably.
The bump is now significantly larger and heavier, which means the forward pull on the lower back and pelvis is greater than before. The centre of gravity has moved further forward still, and the muscles of the lower back, hips, and pelvis are working harder to manage a load they have been gradually adapting to but which has now reached its peak. Fatigue tends to increase as the body is directing more energy towards supporting the pregnancy, and sleep disruption, whether from discomfort, frequent waking, or difficulty finding a comfortable position, compounds that fatigue in ways that affect how the muscles and joints feel through the day.
The ribcage has expanded further to accommodate the growing uterus, which can produce a feeling of tightness or pressure across the mid and upper back. Breathing may feel shallower than usual as space for the diaphragm reduces, and the upper back and neck can become more symptomatic as a result.
Relaxin continues to influence joint mobility and stability, and with the added load of the third trimester, the pelvic joints, hips, and knees can feel less secure and more uncomfortable than they did earlier in the pregnancy.
Lower back and pelvic discomfort are among the most commonly reported MSK experiences in the third trimester, and for understandable reasons. The combination of increased forward load, softened ligaments, and fatigued supporting muscles means the lower back and pelvis are under significant and sustained demand.
For desk workers, the seated position compresses the lower back and can reduce the space available for the bump, which tends to increase discomfort over a long stretch of sitting. Lumbar support is particularly important at this stage. A cushion or rolled towel placed in the curve of the lower back, or a chair with adjustable support, helps maintain a comfortable spinal position without the lower back muscles having to hold it independently.
Seat height is worth reassessing as the bump grows. A seat that is slightly higher than usual, allowing the hips to sit a little above the knees, can reduce the compression on the lower back and make it easier to move in and out of the chair. Armrests that allow the weight of the arms to be supported take some of the load off the upper back and shoulders, which tend to be working harder than usual to compensate for the postural changes lower down.
Movement breaks are more important in the third trimester than at any earlier stage. Standing up and moving briefly every thirty to forty minutes, rather than the forty-five to sixty minutes suggested earlier in pregnancy, gives the lower back and pelvis more frequent opportunities to shift out of the sustained seated position before tension and discomfort build significantly.
The upper back, neck, and shoulders tend to become more symptomatic in the third trimester as the postural chain that began in the lower back and pelvis works its way upward. The increased lower back curve encourages the upper back to round, the shoulders to drift forward, and the neck to extend to keep the head level. For desk workers this pattern is amplified by the screen-facing position, and many people find that neck and upper back tension increases noticeably through the final trimester.
Keeping the screen at a comfortable distance and height, as covered in the second trimester article, remains important. Gentle movement of the neck and upper back through the day, such as slow shoulder rolls, careful neck rotations, and brief chest opening movements, helps manage the tension that accumulates in these areas. Even a few repetitions a couple of times through the working day can make a meaningful difference to how the upper body feels by the end of it.
Sleep disruption is one of the most significant contributors to how the body feels during the third trimester, and it has a direct effect on MSK comfort. As covered in an earlier article in this series, poor sleep lowers the threshold at which the nervous system registers discomfort, which means that the lower back, hip, and pelvic tension that might feel manageable after a good night can feel considerably more prominent after a disrupted one.
Finding a comfortable sleep position becomes increasingly challenging as the bump grows. Side sleeping is generally recommended during the third trimester, with the knees bent and a pillow between them to support the pelvis and reduce the rotational load on the lower back and hips. A pillow under the bump can also help by reducing the gravitational pull on the lower back overnight.
Waking frequently is common in the third trimester and difficult to avoid entirely. Keeping the transition from lying to sitting to standing gentle and unhurried, rather than sitting up quickly or twisting to get out of bed, reduces the load on the pelvic joints and lower back during those overnight movements.
For people who experienced some pelvic girdle discomfort in the second trimester, it is likely to be more pronounced in the third as the load on the pelvic joints increases. For others it may appear for the first time during this phase.
The same principles apply as in the second trimester. Keeping movements symmetrical, sitting to dress, avoiding large steps or standing on one leg where possible, and not carrying heavy loads on one side all help manage pelvic girdle discomfort. Walking at a comfortable pace rather than a brisk one, and taking shorter steps, tends to reduce the rotational demand on the pelvis.
If pelvic girdle discomfort is significant, persistent, or affecting daily function, speaking to a physiotherapist who specialises in pregnancy is worth doing sooner rather than later. Support, targeted exercises, and occasionally a pelvic support belt can make a considerable difference to comfort through the final weeks.
Your VIDA pregnancy assessment can give you more tailored exercises and guidance based on your specific stage and how your body is feeling, and is a good place to start if you want support that goes beyond the general adjustments covered here.
The instinct to rest more as the third trimester becomes more demanding is entirely understandable, and rest is genuinely important. At the same time, remaining gently active tends to support MSK comfort better than reducing movement significantly. The muscles that support the lower back, pelvis, and hips need to stay engaged and mobile to manage the demands being placed on them. Long periods of inactivity allow them to stiffen and fatigue more quickly when activity resumes.
Gentle walking, swimming if accessible, and the exercises in your VIDA pregnancy programme are all appropriate ways to stay active in the third trimester. The key is keeping the level of activity consistent and manageable rather than swinging between periods of significant effort and prolonged rest.
Listening to the body is particularly important at this stage. The third trimester is not a time to push through significant discomfort or try to maintain activity levels from earlier in the pregnancy. It is a time to move regularly, rest adequately, and adjust expectations to meet where the body actually is rather than where it was.